1. Field of the Invention
This invention relates to telescopingly engaged elements, such as tubular elements that define a fluid discharge path and, more particularly, to a connecting system which allows the elements to be maintained operatively connected in a plurality of different relative positions. The invention is further directed to a method of maintaining the elements together using such a system.
2. Background Art
Tubular elements are commonly telescopingly engaged in a plurality of different environments. As one example, tubular elements are engaged in this manner to define a discharge path for forced air developed by blowers used in the landscaping industry. These blowers are made with a number of different configurations, ranging from back mounted to hand held.
In these blowers, telescoping connections are established between: a) tubular sections and fittings on the housing for the mechanism generating the forced air; b) two or more tubular sections joined to produce a combined desired length; and c) tubular sections and end fittings used to control the ultimate discharge pattern at the point of use of the fluid. It is common to construct the telescoped portions of the above components from relatively thin-walled plastic material. The external surfaces of the male portions are dimensioned to be closely received within the surrounding female surfaces at each connection.
Maintenance of each such connection has heretofore been accomplished in a number of different manners. In one mechanism, the male and female surfaces are maintained together solely through frictional forces generated therebetween. In another form, a bayonet-type connection is established between the male and female portions. It is also known to use threaded connections.
Heretofore, problems have been encountered in maintaining the integrity of these connections. Those connections relying entirely on friction may be affected by surface wear after repeated assembly/disassembly processes. The wear may reach the point that one of the sections and/or fittings may blow off during use. This may lead the operator to jury-rig the connections, as by either permanently bonding the same or utilizing tape to hold the elements together. This defeats the desired separation capability for the tubular sections and associated fittings.
The same type of problem may be encountered with the bayonet-type connections and still other connections currently being utilized. With the bayonet-type connections, the repetitive assembly and disassembly steps may wear surfaces to the point that the joined elements become loosely engaged. This may produce undesirable rattle and could potentially result in a separation of parts during use.
The above types of systems present challenges to designers that must balance oft times competing objectives. Cost is always a consideration in the design process. It is know to make the tubular elements by different manufacturing processes. For example, tubular elements may be made using injection molding or blow molding techniques. Generally, closer dimensional tolerances can be maintained using an injection molding process. While tolerances can be maintained fairly closely with blow molding on the external surfaces of these parts, the same accuracy is generally not achievable on the inside surfaces. Variations from optimal dimensions can be significant, particularly with components having closely matched, cooperating male and female surfaces that are maintained together, solely or primarily, by frictional holding forces. If the surface is made so that the connection is too tightly held, separation of the parts may be difficult. If the connection is too loose, the elements are prone to rattling or being inadvertently separated during use.
The industry continues to seek out connecting mechanisms that operate effectively for the useful life of equipment and which at the same time can be produced at a reasonable cost.